Some 500 workers are in quarantine on a large Bavarian farm to contain a mass coronavirus outbreak, German officials said Sunday, as they announced free COVID-19 tests for worried local residents.

A total of 174 seasonal workers have tested positive for the virus since Friday, Werner Bumeder, the district administrator of Dingolfing-Landau, told a press conference.

Most of the seasonal employees come from Hungary, Romania, Bulgaria and Ukraine, he said, and had been working in close proximity harvesting cucumbers at the farm in the municipality of Mamming.

He stressed that the cluster appeared to be limited to “a closed group of people” and had not yet spread to the wider population.

The farm’s 480 employees and managers are all in lockdown on-site, with those who have tested negative staying in separate accommodation from those known to be infected.

The farm itself has been closed off from the outside world with a security team monitoring the quarantine.

Bumeder said the outbreak showed that the farm “did not consistently implement” hygiene regulations aimed at preventing the spread of the deadly virus.

One of the infected employees has had to be hospitalised.

Bavarian Health Minister Melanie Huml said authorities were taking the outbreak “very seriously” and were racing to track down anyone who came into contact with the workers in order to break the chain of infection.

She said health officials would soon begin mass testing at other agricultural businesses in the region.

Residents of Manning who wished to get tested will be able to do so for free, she added, stressing that this could be particularly important for anyone planning to go away on vacation.

Germany has fared better than many of its neighbours in suppressing the virus, reporting just over 200,000 cases and 9,118 deaths to date, according to the Robert Koch Institute for disease control.

But the country has also been hit by repeated coronavirus outbreaks at slaughterhouses, keeping authorities on high alert.

Summer travel is another cause for concern, prompting Germany to announce free tests for holidaymakers returning from abroad.